I never even thought about that folder before,
Whenever I needed to render a animation, I change the location of that Temp file to where I want to save the animation and that's all that's saved. Same deal with the Fluid Temp Folder. I create a new folder for that certain fluid and direct the temp files there. Keeps me organized. ;)

 When I render a frame, I then go to File> "Save Rendered Image" . and save where I want. Looks like I'm going to have to go through the default temp folder now. lol No telling how much stuff is still there from the years. lol

 By The Way, I save my renders/animations/and fluid files on an external Hard Drive. I suggest doing the same.